The purpose of the proposed research program is to define the molecular structure, genetic organization and regulatory function or mechanism of the Drosophila Y chromosome during spermatogenesis and regions of the genome implicated in the action of the insect steroid hormone, ecdysone. Genetic analysis will utilize, respectively, the detection and recovery of male sterile temperature sensitive mutation or lethal mutants defective in ecdysone mediated molting response. The mutants will then be subjected to cytogenetic analysis of, respectively, primary spermatocyte lampbrush loop formation or patterns of polytene chromosome puffing. Biochemical assay of spermiogenesis will qualitatively and quantitatively describe testicular macromolecular biosynthesis in vitro. The analysis of ecdysone action will employ a biochemical characterization and partial purification of larval ecdysone receptor protein(s). The molecular study of gene organization will be accomplished by either chromosome fractionation or the construction and isolation of hybrid recombinant plasmids of E. coli bearing the genetic region of interest; the specific DNA's recovered will be further dissected by bacterial restriction endonuclease fragmentation and DNA/DNA reassociation and also utilized as probes for the assay and analysis of tissue and temporally specific transcription.